1. Field of the Invention
This invention relates generally to telephone communications, and more particularly to telephoning via Voice-over-IP (VoIP) and wireless networks.
2. Description of the Background Art
FIG. 1 shows a prior art telephony system 100 that includes a corporate network 120, a traditional Public Switched Telephone Network (PSTN) 140, and a wireless network 160. System 100 routes a communication 124 from a Caller 122 in corporate network 120 to a wireless network Subscriber 190.
The corporate network 120 includes a traditional Private Branch Exchange (PBX) 128. The PSTN 140 includes a Local Exchange Carrier (LEC) 144, which in turn includes a Central Office (CO) 148. PBX 128, which receives communication 124 from Caller 122, establishes connection 130 to Central Office (CO) 148, which in turn establishes connection 150 to wireless network 160. Those skilled in the art will recognize that, instead of communication 124, a comparable communication may also be initiated by a direct telephone call from a home telephone (not shown). Passing through PBX 128, in addition, PSTN 140 may be replaced by an Integrated Services Digital Network (ISDN).
Wireless network 160 includes a Gateway Mobile Switching Center (GMSC) 164, a Home Location Register (HLR) 166, and a Visited Mobile Switching Center (VMSC) 168. GMSC 164, communicating via connection 171 with a base station (BS) 165 within Subscriber 190's “home” wireless network 160, is the control element for managing wireless network 160, and is responsible for switching cellular cells, providing for backup, interfacing with telephone networks, and monitoring telephony traffic.
A wireless Subscriber 190 may “register” merely by turning on his or her cell-phone. This example assumes that Subscriber 190 is currently registered and is not currently engaged in a call. Upon establishment of connection 150 from CO 148, GMSC 164 via signal path 170 gathers information from HLR 166 to determine how to route connection 150. Note that establishment of connection 150 may involve one or more intermediate exchanges.
Wireless network 160 uses HLR 166 and VMSC 168 to locate Subscriber 190 and thereby establish final wireless connection 180. Each Subscriber belongs to one HLR 166 associated with a cellular operator or a commercial network provider. HLR 166 stores information (accounting, subscribed services, profile information, etc.) about Subscriber 190. HLR 166, via one of several (not shown) VMSCs (i.e. VMSC 168), which report back on signal path 174, keeps track of the location of Subscriber 190. VMSC 168 informs HLR 166 when Subscriber 190 is on the system of VMSC 168, and HLR 166 in turn updates its profile record for the new location of Subscriber 190. When a call is placed to Subscriber 190, HLR 166 determines whether Subscriber 190 is a valid subscriber, and if so, which VMSC 168 is currently serving Subscriber 190. Subsequently HLR 166, via signal path 172, requests routing instructions from VMSC 168 for Subscriber 190. VMSC 168, having received information about Subscriber 190 from HLR 166, assigns a routing number N for connection 150, and then returns this routing number N via signal path 174 to HLR 166. The HLR 166 then returns the routing number N via signal path 176 to GMSC 164. The GMSC 164 uses this routing number N to establish connection 178 to VMSC 168. This step may involve one or more intermediate exchanges and/or networks. Once connection 178 is established with the VMSC 168, wireless connection 180 is completed to Subscriber 190 using standard wireless call processing which is not described herein.
FIG. 2 shows a prior art system 200 comprising a corporate network 120 as in system 100 of FIG. 1, a VoIP Virtual Private Network (VPN) 240, and a wireless network 160 as in system 100 of FIG. 1. System 200 uses VPN 240 instead of PSTN 140 of system 100 to route a communication 124 from a Caller 122 to a wireless network Subscriber 190. Connection 130 is established between PBX 128 and GW-1 242, residing within the VoIP VPN 240.
VoIP VPN 240 includes a Command Center (CC) 244, a Gateway (GW-1) 242, and a second Gateway (GW-2) 246. In the preferred embodiment of the invention, CC 244, GW-1 242, and GW-2 246 are command center and gateway products of Clarent Corporation of Redwood City, Calif. In system 200, as in system 100, instead of communication 124 passing through PBX 128, a comparable communication may also be initiated by a direct telephone call from a home telephone.
The gateways GW-1 242 and GW-2 246 support an Internet Protocol (IP) such as Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) connection via the VoIP VPN 240 to the Internet (not shown). GW-1 242 and GW-2 246 support both telephone-to-telephone communications and PC-to-telephone communications.
The originating exchange PBX 128 within the corporate network 120 (or possibly a Central Office, not shown) determines that VPN 240 is on-net. GW-1 242 via signal path 250 requests routing information from CC 244. CC 244 verifies that connection 130 is allowed and translates the called Subscriber 190's number into an IP address. CC 244 via signal path 252 notifies GW-2 246 about the incoming connection 258, and GW-2 246 via signal path 254 notifies CC 244 of its readiness to accept connection 258. CC 244 via signal path 256 returns the translated IP address to GW-1 242. GW-1 242 establishes connection 258 with GW-2 246. GW-2 246 continues routing based upon the called Subscriber 190's number via path 262 to a GMSC 164 within the called Subscriber 190's home wireless network 160. This step may involve one or more intermediate exchanges and/or networks.
From this point on, standard wireless call processing is used. The GMSC 164 via signal path 170 queries HLR 166 containing the Subscriber 190's profile to determine how to continue routing. This example assumes that the subscriber is registered and is not currently engaged in a call. Registration may occur merely by Subscriber 190 turning on his cell-phone. The HLR 166 determines that the Subscriber 190 is valid and determines which VMSC 168 is currently serving him or her. HLR 166 via signal path 172 queries VMSC 168 for routing instructions. The VMSC 168 determines that Subscriber 190 is registered within its service area and assigns a temporary routing number N. VMSC 168 returns this temporary routing number N via signal path 174 to HLR 166, which in turn returns temporary routing number N via signal path 176 to GMSC 164. The GMSC 164 uses the temporary routing number N to route connection 178 to VMSC 168. This step may involve one or more intermediate exchanges and/or networks. Once the connection is established with VMSC 168, wireless call 180 is completed to Subscriber 190 using standard wireless call processing, which is not described herein.
In both prior art systems 100 and 200, GMSC 164 is fixed in the home service area of Subscriber 190. System 200 changes between using VMSCs 168 in different locations based upon the location of Subscriber 190, and regardless of the subscriber's location, connections are always routed to GMSC 164 before being transmitted to the VMSC 168 closest to the subscriber, generally, and then to Subscriber 190. The GMSC 164 being fixed in the home service area for Subscriber 190 creates inefficiency. For example, suppose Subscriber 190 has a home base in Los Angeles (LA), Calif., and travels to San Francisco (SF), Calif., where Caller 122 resides. Consequently, GMSC 164 is in LA (or some nearby locality) and VMSC 168 is in SF (or some nearby locality). As Caller 122 uses either system 100 or 200 to call Subscriber 190, routing must go from SF to GMSC 164 in LA, then to VMSC 168 in SF, and eventually to Subscriber 190 in SF. As a result, even if Caller 122 and Subscriber 190 are in the same locale of SF, routing must first go through LA before reaching Subscriber 190, who is in SF. Further, in a traditional wireless call as depicted in system 100, Caller 122 would incur two long distance toll charges, one from SF to LA, and one from LA back to SF.
Additionally, VoIP VPN 240 of system 200 loses control of routing. As connection 262 leaves GW-2 246 and enters wireless network 160, the wireless network 160 assumes complete control of routing. Once the connection 262 is passed from VoIP VPN 240 into the wireless network 160, a traditional toll call takes place, even though Caller 124 and Subscriber 190 in this example are both located in SF. The VoIP VPN 240 eliminates the toll leg from SF to LA, but the wireless network 160 still creates a toll call from GMSC 164 in LA to VMSC 168 in SF.
Moreover, in various situations, VoIP VPN 240 would benefit from maintaining control of a call up to the connection 262 with VMSC 168 for providing additional call completion services without being dependent upon wireless network 160.
What is needed, therefore, is a solution that can alleviate the above-discussed deficiencies by eliminating possible and/or unnecessary toll calls.